1. Field of the Invention
The present invention is related to an ultrasonic diagnostic apparatus, a positional information acquiring method, and a computer program product.
2. Description of the Related Art
Among conventional technologies, an ultrasonic diagnostic apparatus is advantageous in its operational ease and noninvasiveness without the possibility of exposure to radiation, to other medical diagnostic imaging devices such as an x-ray diagnostic device and an x-ray computer tomograph. The ultrasonic diagnostic apparatus is therefore widely used in examination and diagnosis of various parts of body tissues such as heart, liver, kidney, mammary gland, and muscles in today's medicine.
The ultrasonic diagnostic apparatus transmits an ultrasonic wave to a subject from an ultrasound probe, and generates an ultrasonic image based on the reflection wave of the ultrasonic wave reflected from the inner tissues of the subject.
In recent examinations incorporating an ultrasonic diagnostic apparatus such as ultrasonic breast examinations that are recommended for early detection of breast cancer, an ultrasound probe needs to be moved and rolled on the breast surface by a doctor or a clinical laboratory technician to find an optimal position for observation of a lesion. Thus, for the doctor to recognize the position of the lesion indicated in an ultrasonic image, it is important to obtain positional information of the ultrasound probe at the time of generating the ultrasonic image.
To obtain the positional information of the ultrasound probe, an ultrasonic diagnostic apparatus has been developed, in which a magnetic field generation coil that generates a magnetic signal is attached to a bed on which a subject lies and the ultrasound probe is provided with a magnetic sensor (see JP-A 2006-246974 (KOKAI) and JP-A 2007-244575 (KOKAI), for example). In such an ultrasonic diagnostic apparatus, the magnetic sensor that detects the magnetic signal generated by the magnetic field generation coil calculates coordinates of the position of the magnetic sensor with respect to the magnetic field generation coil so that the positional information of the ultrasound probe can be obtained.
Furthermore, an ultrasonic diagnostic apparatus in which the ultrasound probe is provided with an optical sensor has also been developed to obtain the positional information of the ultrasound probe (see, for example, “Development of System for Detecting Position of Breast Examination Probe Incorporating Color Sensor”, The 81st Annual Scientific Meeting of the Japan Society of Ultrasonics in Medicine, S283, May, 2008). In such an ultrasonic diagnostic apparatus, the optical sensor reads a color pattern fixed onto the area of the subject that is to be examined so that the positional information of the ultrasound probe can be obtained.
The positional information of the ultrasound probe obtained in this manner is displayed, for example, as a body mark on the monitor together with an ultrasonic image so that the doctor who conducts an image diagnosis easily recognizes the position of the examination region in the ultrasonic image that is being viewed. A body mark is a brief description that roughly indicates the position and orientation of the ultrasound probe that is placed on the subject at the time of generating an ultrasonic image.
According to the above conventional technologies, however, the positional information of the ultrasound probe cannot be easily acquired. More specifically, with the above conventional technologies, because a positional sensor such as a magnetic sensor and an optical sensor needs to be additionally arranged in the ultrasound probe, the structure of the ultrasonic diagnostic apparatus becomes complicated, which increases the cost of production.